Presidential Address. T. Petch. 39 
the groves which were not sprayed with spore solutions than 
in the experimental blocks. In no case has practical benefit 
been observed to result from efforts to increase the efficiency 
of the fungi in groves where they previously occurred. The 
above remarks apply especially to the Aschersonias. With the 
brown fungus, efforts to increase the efficacy have been equally 
disappointing from a practical standpoint. 
“As aresult of the investigations reported herein and of obser- 
vations and experience covering a period of four years the 
authors conclude that there are at present no elements of natural 
control herein dealt with which can be relied upon to give 
satisfactory results. Under present conditions it is unques- 
tionably more profitable to depend upon artificial remedies.”’ 
The Florida results thus agree with those of other experiments 
of the same character, and at the present day after 30 years’ 
trial there is no instance of the successful control of any insect 
by means of fungus parasites. If the entomogenous fungi 
already exist in a given area, practically no artificial method of 
increasing their efficacy is possible. If they are not present, 
good may result from their introduction, if local conditions are 
favourable to their growth, but, on the other hand, their absence 
would appear to indicate unfavourable conditions. 
It would seem that a fungus makes little progress until the 
insects are excessively numerous, either locally or generally, 
when for reasons not known an epidemic of fungus disease 
breaks out. And in this connection it may be noted that the 
apparently successful experiments in inducing a more rapid 
dissemination of an entomogenous fungus have usually been 
made during such an epidemic. 
Morrill and Back’s statement that Aschersonia Aleyrodis, etc., 
have controlled the white fly to the extent of about one-third 
of a complete remedy is apparently to be interpreted that an 
epidemic of fungus disease among the scale insects occurs every 
three years. Where an insect is always present, these epidemics 
appear to occur at definite intervals; and where the occurrence 
of the insect is discontinuous, they appear to occur at a definite 
period from the first appearance of the insect. The Wilt disease 
of the Tea Tortrix of Ceylon (Homona coffearia), though not a 
fungus disease, gives a notable illustration of that. The occur- 
rence of that insect as a pest is discontinuous. In the first year 
of its appearance in any locality, the insect increases without 
any check; in the second year, Wilt disease attacks a small 
proportion of the caterpillars; in the third year, it practically 
kills out every one. In the case of Cephalosporium Lecanit on 
Lecanium viride on coffee in Ceylon, an epidemic of fungus 
disease occurs in the same locality during each rainy season; 
